The invention is directed to a spraying apparatus. For example, the invention is directed to an atomizing sprayer which is used to atomize a liquid into a mist for application to an article. Such a sprayer can be used, for example, to atomize paint to be applied to an article. The sprayer can operate electrostatically, wherein there is a difference in electrical potential between the liquid and the article. For example, a charge can be applied to the paint and the article can be grounded, such that the atomized liquid is attracted through electrical forces to the article.
One such conventional sprayer is a rotary atomizer which rotates at a high rate of speed around a central axis in order to atomize a liquid into a mist. A source of electrical power can be connected to such a rotary atomizer in order to charge the liquid as it flows through the rotary atomizer such that the mist produced by the rotary atomizer will be electrically attracted to the article to be coated. For example, when painting an automobile, conventional rotary atomizers are provided with a charge of a 100,000 volts and the car to be painted is grounded. As paint passes through such an electrically charged rotary atomizer, the resulting mist picks up the charge and is therefore attracted to the automobile.
Conventional rotary atomizers are bell-shaped and made from materials such as aluminum. Some versions of these conventional atomizers are provided with a plurality of channels or grooves near an outer edge of the atomizer. These grooves are intended to separate the paint into uniform streams within the grooves. After passing through these grooves, the paint is atomized at a point beyond an outer edge of the atomizer. Other conventional atomizers have intersecting grooves which are used to mix multi-component paint prior to atomization of the paint.
These conventional atomizers have many drawbacks. For example, when a 100,000 volt charge is applied to the atomizer, and therefore to the liquid flowing therethrough, the charge of the mist created by the atomizer is significantly less than 100,000 volts at a point where the mist makes contact with the article. For example, in a conventional atomizer spaced a conventional distance of 18 inches from an automobile with a charge of 100,000 volts applied to the atomizer, the charge on the resulting mist as it reaches the automobile is typically between 16,000 and 18,000 volts. Thus, a significant portion of the 100,000 volts applied to the paint via the atomizer is dissipated. This charge dissipation is a significant drawback, since the charge on the atomized mist is directly proportional to the amount of attraction of the mist to the grounded article. If an apparatus can provide the mist with a higher charge, a greater percentage of the mist will adhere to the article and less paint will be required in order to adequately cover the article.
Another drawback of conventional aluminum rotary atomizers is that the atomizer is easily damaged. For example, if such an atomizer experiences a relatively small force, as may occur when the atomizer is dropped a few feet onto a hard factory floor, the atomizer can be easily damaged, requiring replacement or costly repair.
Another drawback of conventional aluminum rotary atomizers is that they are not easily cleanable during a changeover from spraying one form of liquid or paint to spraying another form of liquid or paint. For example, if such a conventional rotary atomizer is used in a typical factory environment to paint a first car blue and a next car red, the atomizer must be thoroughly cleaned between the time it paints the first car and the time it paints the second car. Atomizer cleaning is typically accomplished by running cleaning fluid through the atomizer to wash out residue from the first painting. Conventional rotary atomizers require a significant amount of cleaning fluid to accomplish this cleaning because the paint mist adheres to the aluminum surface of the atomizer. When paint adheres to the aluminum surface of a conventional rotary atomizer, the atomizer does not clean very easily. Another reason for this drawback of conventional rotary atomizers is that conventional rotary atomizers do not have a structure which optimally distributes cleaning fluid when passed therethrough during the cleaning process.